1. Field of the Invention
The present invention pertains to printed circuit board packaging technology, and, more particularly, to a method and apparatus for powering a module, mounted on the printed circuit board, directly from a power distribution bus rather than powering the module from the power distribution bus by way of the printed circuit board.
2. Description of the Prior Art
The computers of the future will require a high throughput performance. High performance is measured in terms of cycle time and the number of cycles per instruction. However, in order to achieve this high performance, the number of circuits on an integrated circuit chip must increase. Consequently, the number of integrated circuit chips must also increase. The introduction of high density integrated circuit packages, such as a Thermal Conduction Module, has provided for the increased number of integrated circuit chips necessary to produce the required high performance.
However, with the introduction of these high density integrated circuit packages, two undesirable side effects are noticeable: (1) the power dissipated by a package is higher than previously experienced, and (2) the required current supplied to the package has increased significantly. These high circuit density integrated circuit packages necessitate the use of a large number of input/output (non-signal) pins to power the chips and to maintain power losses and voltage drops at reasonable levels. This requirement for more pins is compounded by the simultaneous demand for an increased number of input/output signal pins required to conduct the necessary signals to the increased number of circuits on the chips.
Furthermore, the demand for an increased number of circuits renders difficult the design of a modular or granular system. If a system is highly modular or granular in nature, it is easy to maintain and service by field representatives.
In prior art printed circuit board packaging system designs, a module, such as module 10 shown in FIG. 1, has a plurality of integrated circuit chips 10a mounted thereon. Referring to FIG. 2, the module 10 is mounted on a printed circuit board 12, the module being connected to various power distribution planes 12a within the board. The planes 12a are connected to a power distribution bus 14 thereby carrying the required current and providing the required voltage to the module 10 as necessary to power the chips 10a mounted on the module. The module 10 includes a multitude of input/output pins 10b connected to the power distribution planes 12a in the printed circuit board 12 for conducting the voltage and current to the chips 10a. Since the number of circuits on a chip has increased and the number of chips mounted on a module has increased in response to the demand for increased performance of large-scale computers, the number of required pins on the module has also increased, these pins including signal pins to provide the necessary information signal to the chips and power distribution pins to provide the necessary voltage and current to power the chips. Since the number of required pins has increased, the number of power distribution planes in the printed circuit board also increased. Therefore, the thickness of the board has increased. As a result of the increased board thickness, greater power losses are experienced. Board manufacturing complexity also increases as board thickness increases.
Furthermore, due to the increased number of pins, the module must be larger to accommodate the required number of pins. However, the trend, in the design of a computer system, is toward miniaturization of computer system components, not toward enlarging the size of these components.
Therefore, the prior art packaging system could not meet the demand for an increased number of circuits and a resultant increase in the number of integrated circuit chips mounted on a module and, simultaneously, minimize its power losses as well as meet the demand for the miniaturization of computer system components. Another packaging system design is needed to simultaneously achieve the following desired objectives, that is, to increase the performance associated with a computer system, to minimize the power losses associated with the computer system components, and to maintain the trend toward the miniaturization of the computer system components.